The invention relates to a jig system adapted for connection to an intramedullary nail, wherein the intramedullary nail is implanted in a fractured bone, such as a tibia or a femur, the implantation being such as to have the nail extend distally and proximally with respect to the fracture, in reinforcement of fractured parts of the bone that have been re-aligned or merely are to be held in alignment for the course of healing repair.
Intramedullary nails of the character indicated are either solid or hollow, but they are customarily prepared with two spaced parallel holes that extend diametrically across the nail near the distal end of the nail and with two spaced holes of similar nature, but not necessarily parallel, near the proximal end of the nail. These holes are formed to accept bone screws, and when the nail has been installed, its bone-screw holes are said to be "blind" in terms of the bone-drilling alignment that must be achieved. The problem has always been one of assuring correct alignment for drilling to accept a bone screw driven through bone for anchoring passage through the intramedullary nail. The traditional technique for assuring blind drill alignment with the bone-screw holes of an intramedullary nail involves use of x-rays, which of course pose well-known dangers from cumulative exposure; and to assure adequate safety for operating personnel, the use of x-rays is, to say the least, cumbersome, thus contributing to the expense of a good intramedullary-nail installation.
The proximal end of the nail is formed for anti-rotational keyed and detachably fixed connection to jig structure that is intended to aid in orientation of drill guides in the hope of achieving a correct alignment with each drill hole, the customary technique of ascertaining alignment being by use of x-rays.
One of the problems of locating a bone-screw hole in an installed intramedullary nail is the practical fact that the nail may have undergone a slight bend in the course of implantation, so that such holes at the distal end of the nail no-longer have precisely the same location with respect to the proximal end, as was the case prior to nail implantation. Thus, any jig structure connected to the proximal end has had to rely on x-rays for assurance of alignment.
In an effort to avoid x-ray dependence in solving the problem of locating blind bone-screw holes in an installed intramedullary nail, U.S. Pat. No. 5,281,224 and pending U.S. Pat. No. 5,433,720 have proposed magnetic detection, in the scanning displacement of a detection system across the distal region of an installed nail, to locate the central axis of the nail; but in the present state of development, such techniques have been clinically awkward, achieving less than the accuracy that is required.
Also in an effort to avoid x-ray dependence in solving the problem of locating blind bone-screw holes in an installed intramedullary nail, U.S. Pat. No. 5,620,449, filed Mar. 8, 1995, addresses the problem by purely mechanical techniques which involve a drill jig adapted for connection to the proximal end of the particular intramedullary nail selected for implantation in a patient's fractured bone; the distal end of the intramedullary nail has a customary pair of longitudinally spaced bone-screw or bolt holes, the axes of which locally intersect the longitudinal axis of the intramedullary nail. The drill jig is configured to position two geometric axes in generally quadrature relation to each other and respectively generally perpendicular to the longitudinal axis of the nail; one of these two axes is longitudinally positioned for alignment with at least one of the distal bolt holes of the intramedullary nail, while the other of these two axes is in nearby longitudinal offset from said one of the two axes. A contact rod is positionable by the guide on said other of these two axes, with special provision by way of a selectable shim, whereby it can be known that when the contact end of the rod is in contact with the selected intramedullary nail, the said one of these two axes is truly aligned (and is therefore adapted for true drill-guide alignment) with at least one of the bone-screw holes of the selected intramedullary nail. It should be noted that the selected shim for contact-rod positioning is designed to truly compensate for the local radius of the intramedullary nail, so that when contacted by the contact rod, the intramedullary nail will have automatically positioned at least one of its bone-screw holes in true alignment with a drill-guide axis.
While much can be said for the jig system of said pending U.S. application, it might be subject to criticism by the surgeon who is equipped for operation on different patients who he determines to require intramedullary nails of different diameter, e.g., as between the young and the adult of the surgeon's patients.